1. Field of the Invention
The present invention relates to a method for generating a process control algorithm in a process control system, and more particularly, to a method for generating a control algorithm on a graphical user interface of a function block diagram editor and automatically converting the created control algorithm to executable structured control codes.
2. Description of the Prior Art
In the field of massive process control, there have been continuous efforts to establish an automatic control system by using a digital computer. For example, a crane control system controls three types of transmissions (that is, a gantry, a trolley and a hoist) and various driving devices (for example, a rope tensioner and a spreader manipulator) in response to operation commands of an operator from an input device. To perform process control by using such a multifunctional controller, a user program is needed which is a control algorithm adapted to an object system to be controlled. High level program languages such as C.sup.++ and PASCAL can be used to build such control algorithms. However, they are too general and complex for a field user. Moreover, precise knowledge of the details of related hardware is required to implement necessary hardware functions.
To solve these problems, a programmable logic controller has been used thus far, wherein a ladder diagram is used as a graphical control language. However, the programmable logic controller is known to be unsuitable as a process controller which performs not only sequential control functions according to a process flow but also loop control functions, such as rope tension control and operation speed setting of driving devices which should be done in a timely manner. Moreover, the complexity of the ladder diagram increases dramatically as the size of the system increases, thereby rendering it almost impossible to correct any errors encountered in the course of creating the control algorithm.